The present invention relates in general to methods and apparatus for well completion, re-completion, servicing or workover, and in particular to methods and apparatus for well completion, re-completion, servicing or workover without the assistance of a service rig.
Subterranean wells that are drilled to produce oil or gas must be prepared for production and reworked or serviced from time to time. Wells may require reworking or service for a number of reasons.
The preparation of subterranean wells for the production of oil and gas is a complex process which requires specialized equipment that is expensive to purchase, operate and maintain. Because many wells are now drilled in marginal bearing formations, the wells may require fracturing or some other form of stimulation treatment before production becomes economical. The preparation of a new well for production is called well completion. Well completion generally involves wellhead installation, casing perforation, production tubing installation, etc. If the well is in a marginal production zone, the well may require stimulation after casing perforation. Traditionally, after a well was stimulated, it was xe2x80x9ckilledxe2x80x9d by pumping in overbearing fluids such as drilling mud to permit a wellhead to be put on the casing. This practice is losing favor, however, as it has been observed that killing a well may reverse much of the benefit gained by the stimulation process.
It is also common practice now to re-complete hydrocarbon wells to extend production. Hydrocarbon wells are re-completed using drilling and/or production stimulation techniques well known in the art. Re-completion generally requires the same tools and equipment required for well completion.
Well workover generally entails well treatments to stimulate hydrocarbon production in wells in which production has dropped below an economically viable level. Such treatments may include high pressure fracturing and/or acidizing. During well stimulation it is common knowledge that it is preferable to introduce stimulation fluids into the well at the highest possible transfer rate. Consequently, it is now common practice to remove the wellhead and pump stimulation fluids through the blowout preventers and into the casing. In order to protect the blowout preventers from washout, blowout preventer protectors have been invented, as described, for example, in Applicant""s U.S. Pat. No. 5,819,851 which issued on Oct. 13, 1998, the specification of which is incorporated herein by reference.
Generally, when a well completion, re-completion or workover is required a service rig is brought in and set up to remove the wellhead components, shift or remove production tubing, etc. Such rigs have a derrick or mast that supports pulleys or block and tackle arrangements operable to pull the wellhead from the well, shift the production tubing string or remove it from the well bore, run a production tubing string or other tools into the well bore, unseat and reseat the packers and/or anchors in the well bore, etc.
Although rigs are very useful and adapted to perform any job associated with manipulating well components during a well completion, re-completion, or workover, they are complex assemblies of equipment that are expensive to construct and maintain. Besides, they generally require a crew of four, so they are expensive to operate. Rigs are also usually only intermittently during a well completion, re-completion, servicing or workover operation. Consequently, there is normally considerable idle time on such rigs. This is uneconomical and contributes to the cost of production.
Wells may require service to replace worn or faulty valves, replace or renew seals, to remove a flange from the wellhead, or insert a new flange into the wellhead. Many of these operations are relatively simple and do not require much time. It is therefore uneconomical to bring in and set up a service rig to perform the well service operation.
There is therefore a need for a method and an apparatus that is adapted to provide the functionality required for most well completion, re-completion, servicing and workover jobs, without the requirement of a service rig.
It is therefore an object of the invention to provide an apparatus that is adapted to perform a variety of operations associated with subterranean well completion, re-completion, servicing or workover without the use of a service rig.
It is another object of the invention to provide a wellhead spool for pressure containment that may be used for rigless completion, re-completion, servicing or workover a subterranean well.
It is a further object of the invention to provide methods for rigless completion, re-completion, servicing or workover of a subterranean well.
The invention therefore provides an apparatus that includes a spool for pressure containment that can be mounted to a tubing head spool to permit a well to be completed, re-completed, serviced or worked over without the use of a service rig. The spool supports prime movers, such as hydraulic cylinders, ball jacks or screw jacks, used to insert tubulars, tools or wellhead components into or remove them from the well bore. The spool may be a blowout preventer (BOP) or a high pressure valve. The prime movers may be supported in bores that extend through a body of the spool, or by brackets welded to sidewalls of the spool.
The apparatus in accordance with the invention permits most well completion, re-completion, service and workover operations to be performed without the use of a service rig. Considerable savings are therefore realized.